Results from the 2015 AP Statistics Exam

Results from the 2015 AP Statistics Exam

Jessica Utts, University of California, Irvine Chief Reader, AP Statistics jutts@uci.edu

The six free-response questions

Question #1: Accountant salaries five years after hire

Compare boxplots; pros and cons of working for each company

Question #2: Restaurant discounts for 20% of bills

Use confidence interval to test value; effect of change in n

Question #3: Automated teller machines at the mall

Probability and expected value for discrete random variable

Question #4: Aspirin and colon cancer

Two sample z-test for comparing proportions

Question #5: Heights and arm spans

Interpret scatter plots and lines; regression prediction

Question #6 (investigative task): Tortilla diameters

Compare sampling methods; sampling distributions

2015 AP Statistics Exam Results

Plan for each question

State question Present solution Describe common student errors Suggest teaching tips Report average score (all at the end)

2015 AP Statistics Exam Results

Question 1 Accountant salaries five years after hire

Compare boxplots; pros and cons of working for

each company

Question #1

Two large corporations, A and B, hire many new college graduates as accountants at entry-level positions. In 2009 the starting salary for an entrylevel accountant position was $36,000 a year at both corporations. At each corporation, data were collected from 30 employees who were hired in 2009 as entry-level accountants and were still employed at the corporation five years later. The yearly salaries of the 60 employees in 2014 are summarized in the boxplots below.

2015 AP Statistics Exam Results

Question 1, continued

(a) Write a few sentences comparing the distributions of the yearly salaries at the two corporations.

(b) Suppose both corporations offered you a job for $36,000 a year as an entry-level accountant. (i) Based on the boxplots, give one reason why you might choose to accept the job at corporation A. (ii) Based on the boxplots, give one reason why you might choose to accept the job at corporation B.

2015 AP Statistics Exam Results

Question 1(a) Solution

The median salary is the same for both companies.

The range and interquartile range of the salaries are much larger for Corporation A than for Corporation B.

Corporation A has two outlier salaries at the high end, while Corporation B has no outliers.

2015 AP Statistics Exam Results

Question 1(b) Solution

Q: Based on the boxplots, give one reason why you might choose to accept the job at Corporation A.

Five years after starting, at least 3 out of 30 (10%) of the salaries at Corporation A are higher than the maximum salary at Corporation B. If I accept the offer from Corporation A, I might be able to make a higher salary at A than at B.

2015 AP Statistics Exam Results

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